Animal Coordination, Control and Homeostasis Flashcards
What are hormones?
Chemicals released directly into the blood which are then carried to other parts of the body (their target organs)
How are hormones produced?
Hormones are produced/secreted by endocrine glands - these make up your endocrine system
What hormones does the pituitary gland produce?
- hormones that regulate body conditions
- called the “master gland” as the hormones act on other glands, stimulating the release of other hormones
- e.g. FSH and LH released here
What hormones do the ovaries produce?
- oestrogen
What hormones does the thyroid gland produce?
- thyroxine (involved in regulating rate of metabolism, heart rate and temperature)
What hormones do the adrenal glands produce?
- adrenaline (used to prepare the body for fight or flight response)
What hormones does the pancreas produce?
- insulin (regulates blood glucose level)
What hormones do the testes produce?
- testosterone (controls puberty and sperm production)
What’s the difference between neurones and hormones?
- hormones have slower action
- hormones act for a LONGER TIME
- hormones act in a more general way
What does adrenaline do to prepare you for “fight or flight”?
- adrenaline binds to receptors in the heart so heart muscle contracts more frequently - increasing blood flow to muscles so more oxygen and glucose for respiration
- adrenaline binds to receptors in the liver, causing the break down of glycogen stores to release glucose
(- body sends nervous impulses to adrenal glands which respond by secreting adrenaline)
How is hormone release affected by negative feedback?
negative feedback systems are used by the body to control the level of hormones in the blood - when levels of a substance go above/below normal level - response triggered to bring back to normal (e.g. thyroxine)
How is thyroxine an example of a negative feedback system?
- blood thyroxine levels are lower than normal
- this stimulates the hypothalamus to release TRH (thyrotropin releasing hormone)
- TRH stimulates pituitary gland to release TSH (thyroid stimulating hormone)
- TSH stimulates release of thyroxine so blood thyroxine level goes back to normal
- if too high - release of TRH from hypothalamus is inhibited - reduces production of TSH and then thyroxine
What is the menstrual cycle?
the monthly sequence of events in which the female body releases an egg and prepares the uterus in case the egg is fertilises
What are the four stages of menstruation?
Stage 1 (1-4): lining of uterus breaks down and is released Stage 2 (4-14): uterus lining is repaired until thick spongy layer of blood vessels is formed - ready for egg to implant Stage 3 (14): an egg develops and is released from the ovary Stage 4 (14-28): lining is maintained - if no egg is fertilised on day 28, the process starts again
What does FSH do during menstruation?
(follicle-stimulating hormone)
- released by pituitary gland
- causes follicle to mature in one of the ovaries
- stimulates oestrogen production
What does oestrogen do during menstruation?
oestrogen:
- released by ovaries
- causes uterus lining to thicken and grow
- large amount stimulates an LH surge
What does LH do during menstruation?
(luteinising hormone)
- released by pituitary gland
- the LH surge stimulates ovulation - follicle ruptures and egg is released - remains of the follicle develops into a structure called a corpus luteum (secretes progesterone)
What does progesterone do during menstruation?
progesterone:
- released by the corpus luteum after ovulation
- maintains uterus lining
- inhibits release of FSH and LH
- when progesterone levels fall, and there is a low oestrogen level, the uterus lining breaks down - low progesterone allows FSH to increase (and the cycle starts again)
How are hormones used to treat infertility?
- Clomifene therapy
- IVF
What happens in clomifene therapy?
- clomifene is a drug given to women who don’t ovulate
- clomifene causes more FSH and LH to be released into the body (stimulating egg maturation and ovulation)
- knowing when an egg will ovulate means a couple can have intercourse in this time to improve pregnancy chances
What happens in IVF?
- eggs collected from ovaries and fertilised in a lab
- eggs grown into embryos - 1-2 of these are transferred into the uterus to improve chance of pregnancy - FSH and LF are given before egg collection to stimulate egg production
- example of Assisted Reproduction Technology (ART) - fertility treatment involving eggs handled outside the body
How can hormones be used as contraceptives?
- oestrogen can be used to prevent the release of an egg (keeping levels permanently high inhibits FSH production and eventually stops egg development)
- progesterone reduces fertility - e.g. by stimulating production of cervical mucus, preventing sperm getting through the cervix to the egg (e.g. mini-pill and contraceptive injection)
- combined pill and contraceptive patch both use oestrogen + progesterone mix
- barrier methods of contraception can also be used (e.g. condoms, diaphragms etc)
What are the effects of hormonal contraceptives?
- generally more effective than barrier methods - also mean people dont have to think about contraception when having intercourse
- side effects such as headaches, acne and mood swings - no protection against STIs
What is homeostasis?
Maintaining a constant internal environment - important because cells and enzymes need to be in right conditions to function